// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Command make_builtin_vdlroot runs at jiri go generate time. It emits a Go
// source file called builtin_vdlroot.go containing a gzip'd version of all the
// core VDL types required by the VDL tool. This allows the VDL tool to run
// 'standalone' (i.e. without access to the Vanadium source code).
//
// +build ignored

package main

import (
	"archive/tar"
	"compress/gzip"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"os"
	"path/filepath"
)

const (
	outputPreamble = `// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// This file is automatically generated, your changes will be lost.
// See make_builtin_vdlroot.go.

package main

//go:generate jiri go run make_builtin_vdlroot.go

const (
	// builtinVDLRootData contains the raw bytes for a gzip'd tarball, containing
	// the vdlroot standard packages required to run the vdl tool.
	builtinVDLRootData = "`
	outputFooter = `"
)
`
)

// writeBytes writes the given bytes to the given writer, returning an error if
// the underlying Write fails or if the number of bytes written is not equal to
// len(content).
func writeBytes(out io.Writer, content []byte) error {
	n, err := out.Write(content)
	if err == nil && n != len(content) {
		err = fmt.Errorf("wrote an unexpected number of bytes, wanted %d, wrote %d", len(content), n)
	}
	return err
}

// hexWriter writes data as a sequence of \xAB constants.
type hexWriter struct {
	w io.Writer
}

func (w hexWriter) Write(data []byte) (int, error) {
	for index, b := range data {
		if _, err := fmt.Fprintf(w.w, `\x%02X`, b); err != nil {
			return index, err
		}
	}
	return len(data), nil
}

// writeVDLRootData creates a gzip'd tar file containing all of the VDL files
// in vdlroot. The data is encoded as base64. Does not close out.
func writeVDLRootData(out io.Writer) error {
	jiriRoot := os.Getenv("JIRI_ROOT")
	if jiriRoot == "" {
		return fmt.Errorf("JIRI_ROOT is not set")
	}
	srcDir := filepath.Join(jiriRoot, "release", "go", "src")
	vdlroot := filepath.Join(srcDir, "v.io", "v23", "vdlroot")
	hexWriter := hexWriter{out}
	gzipWriter := gzip.NewWriter(hexWriter)
	tarWriter := tar.NewWriter(gzipWriter)
	walkFn := func(path string, info os.FileInfo, err error) error {
		if filepath.Ext(path) == ".vdl" || filepath.Base(path) == "vdl.config" {
			content, err := ioutil.ReadFile(path)
			if err != nil {
				return err
			}
			relPath, err := filepath.Rel(srcDir, path)
			if err != nil {
				return err
			}
			header := tar.Header{
				Mode: int64(0644),
				Name: relPath,
				Size: int64(len(content)),
			}
			if err := tarWriter.WriteHeader(&header); err != nil {
				return err
			}
			return writeBytes(tarWriter, content)
		}
		return nil
	}
	if err := filepath.Walk(vdlroot, walkFn); err != nil {
		log.Printf("Walk() failed: %v", err)
	}
	if err := tarWriter.Close(); err != nil {
		log.Printf("Close() of tar file failed: %v", err)
		return err
	}
	if err := gzipWriter.Close(); err != nil {
		log.Printf("Close() of gzip file failed: %v", err)
		return err
	}
	return nil
}

func main() {
	filename := "builtin_vdlroot.go"
	f, err := os.Create(filename)
	if err != nil {
		log.Printf("Create(%q) failed: %v", filename, err)
		os.Exit(1)
	}
	defer f.Close()
	if err := writeBytes(f, []byte(outputPreamble)); err != nil {
		os.Exit(1)
	}
	if err := writeVDLRootData(f); err != nil {
		os.Exit(1)
	}
	if err := writeBytes(f, []byte(outputFooter)); err != nil {
		os.Exit(1)
	}
}